Method for preparing acetic acid by catalyst

Abstract

A method for preparing acetic acid by catalyst including the following steps is provided, S1. preparing the hydrotalcite carrier by hydrothermal method; S2. ion exchange; S3. liquid phase reduction; S4. placing the CoPd/LDH catalyst obtained in S3 in a two-channel fixed bed step-by-step continuous reactor, carrying out the reaction at 100-400° C. and 0.1-20 MPa, synthesizing acetic acid by alternating feeding of CH 4 +H 2 +H 2 O and CO 2 +H 2 +H 2 O, with the alternating time of 50-300 s. The present invention replaces the traditional process of acetic acid production including the steps of methane and carbon dioxide reforming to produce syngas. The process flow is short, the reaction conditions are mild, and the energy consumption and cost are greatly reduced.

What is claimed is: 
     
         1 . A method for preparing acetic acid by a catalyst,
 S1. preparing a hydrotalcite carrier by a hydrothermal method: mixing MgCl 2 ·6H 2 O, AlCl 3 ·6H 2 O, and urea according to a molar ratio of (1-5):(1-5):(1-7) to obtain a resulting mixture and dissolving the resulting mixture in methanol to obtain a resulting solution, after stirring the resulting solution evenly, sealing a stirred solution in a polytetrafluoroethylene lining for a hydrothermal reaction, centrifuging a white precipitate obtained by the hydrothermal reaction, washing a centrifuged white precipitate with a first deionized water and a first ethanol, drying a washed white precipitate at 50-120° C. for 10-24 h to obtain a hydrotalcite carrier MgAl-LDH;   S2. an ion exchange: dispersing the hydrotalcite carrier MgAl-LDH obtained in S1 in a deionized water containing a metal salt to obtain a MgAl-LDH dispersed solution, after stirring and exchanging the MgAl-LDH dispersed solution, centrifuging a resulting MgAl-LDH dispersed solution to obtain a centrifuged precipitate, collecting the centrifuged precipitate and washing the centrifuged precipitate with water to obtain a washed precipitate;   S3. a liquid phase reduction: dispersing the washed precipitate obtained in S2 in a NaBH4 aqueous solution to obtain a precipitate dispersed solution, after stirring and reducing the precipitate dispersed solution for 0.1-2 h, washing a reduced solution with a second deionized water and a second ethanol respectively to obtain a washed product, after drying the washed product to obtain a dried product, roasting the dried product in an inert atmosphere for 1-5 h to obtain a CoPd/LDH catalyst;   S4. placing the CoPd/LDH catalyst obtained in S3 in a two-channel fixed bed step-by-step continuous reactor, carrying out a reaction at 100-400° C. and 0.1-20 MPa, synthesizing the acetic acid by an alternating feeding of CH 4 +H 2 +H 2 O and CO 2 +H 2 +H 2 O, with an alternating time of 50-300 s.   
     
     
         2 . The method for preparing the acetic acid by the catalyst according to  claim 1 , wherein in S1, a temperature of the hydrothermal reaction is 100-200° C., and a reaction time is 5-24 h. 
     
     
         3 . The method for preparing the acetic acid by the catalyst according to  claim 1 , wherein in S1, a molar ratio of Mg:Al in the hydrotalcite carrier MgAl-LDH is (1-5):(1-5). 
     
     
         4 . The method for preparing the acetic acid by the catalyst according to  claim 1 , wherein in S2, the metal salt is one or more of a cobalt salt, a palladium salt, and a platinum salt, and an exchange time is 1-5 h. 
     
     
         5 . The method for preparing the acetic acid by the catalyst according to  claim 4 , wherein in S2, the metal salt is the cobalt salt comprising K 3 [Co(CN) 6 ]. 
     
     
         6 . The method for preparing the acetic acid by the catalyst according to  claim 4 , wherein in S2, the metal salt is the palladium salt comprising Na 2 PdCl 4    
     
     
         7 . The method for preparing the acetic acid by the catalyst according to  claim 4 , wherein in S2, the metal salt is the platinum salt comprising K 2 PtCl 6 . 
     
     
         8 . The method for preparing the acetic acid by the catalyst according to  claim 1 , wherein in S3, a drying temperature is 50-120° C., a roasting temperature is 100-200° C., and the inert atmosphere is N 2 , Ar, and He. 
     
     
         9 . The method for preparing the acetic acid by the catalyst according to  claim 1 , wherein in S4, when CH 4 +H 2 +H 2 O and CO 2 +H 2 +H 2 O reaction gases are fed alternately, flow rates are as follows: a flow rate of CO 2  is 10-50 mL·min −1 , a flow rate of CO 2  mixed with H 2  is 5-20 mL·min −1 , and a flow rate of CO 2  mixed with H 2 O is 0-0.3 mL·min −1 , a flow rate of CH 4  is 10-50 mL·min −1 , a flow rate of CH 4  mixed with H 2  is 1-5 mL·min −1 , and a flow rate of CH 4  mixed with H 2 O is 0-0.2 mL·min −1 .